How Two Trailblazing Psychologists Turned the World of Decision Science Upside Down

After his book Moneyball became a best-seller, Michael Lewis learned that many of the ideas it presented to the general public had actually been introduced decades earlier by a pair of Israeli psychologists: Daniel Kahneman and Amos Tversky. In an adaptation from his new book, Lewis investigates their story, and the intense bond between these radically different men.

Amos Tversky and Daniel Kahneman toast to their partnership in the 1970s.

Courtesy of Barbara Tversky.

Back in 2003, I published a book called Moneyball, about the Oakland
Athletics’ quest to find new and better ways to value baseball players
and evaluate baseball strategies.

The team had less money to spend on players than other teams did, and so its management, out of necessity, set about rethinking the game. In both new and old baseball data—and the work of people outside the game who had analyzed that data—the Oakland front office discovered what amounted to new baseball knowledge. That knowledge allowed them to run circles around the managements of other baseball teams. They found value in players who had been discarded or overlooked, and folly in much of what passed for baseball wisdom. When the book appeared, some baseball experts—entrenched management, talent scouts, journalists—were upset and dismissive, but a lot of readers found the story as interesting as I had. A lot of people saw in Oakland’s approach to building a baseball team a more general lesson: If the highly paid, publicly scrutinized employees of a business that had existed since the 1860s could be misunderstood by their market, who couldn’t be? If the market for baseball players was inefficient, what market couldn’t be? If a fresh analytical approach had led to the discovery of new knowledge in baseball, was there any sphere of human activity in which it might not do the same?

In the past decade or so, a lot of people have taken the Oakland A’s as their role model and set out to use better data, and better analysis of that data, to find market inefficiencies. I’ve read articles about Moneyball for Education, Moneyball for Movie Studios, Moneyball for Medicare, Moneyball for Golf, Moneyball for Farming, Moneyball for Book Publishing, Moneyball for Presidential Campaigns, Moneyball for Government, Moneyball for Bankers, and so on. But the enthusiasm for replacing old-school expertise with new-school data analysis was often shallow. When the data-driven approach to high-stakes decision-making did not lead to immediate success—and, occasionally, even when it did—it was open to attack in a way that the old approach to decision-making was not. In 2004, after aping Oakland’s approach to baseball decision-making, the Boston Red Sox won their first World Series in nearly a century. Using the same methods, they won it again in 2007 and 2013. But in 2016, after three disappointing seasons, they announced that they were moving away from the data-based approach and back to one where they relied upon the judgment of baseball experts. (“We have perhaps overly relied on numbers,” said owner John Henry.)

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The writer Nate Silver for several years enjoyed breathtaking success predicting U.S. presidential-election outcomes for The New York Times, using an approach to statistics he learned writing about baseball. For the first time in memory, a newspaper seemed to have an edge in calling elections. But then Silver left the Times and failed to predict the rise of Donald Trump—and his data-driven approach to predicting elections was called into question . . . by The New York Times!

I’m sure some of the criticism of people who claim to be using data to find knowledge, and to exploit inefficiencies in their industries, has some truth to it. But whatever it is in the human psyche that the Oakland A’s exploited for profit—this hunger for an expert who knows things with certainty, even when certainty is not possible—has a talent for hanging around. It’s like a movie monster that’s meant to have been killed but is somehow always alive for the final act.

And so, once the dust had settled on the responses to my book, one of them remained more alive and relevant than the others: a review by a pair of academics, then both at the University of Chicago—an economist named Richard Thaler and a law professor named Cass Sunstein. Thaler and Sunstein’s piece, which appeared on August 31, 2003, in The New Republic, managed to be at once both generous and damning. The reviewers agreed that it was interesting that any market for professional athletes might be so screwed up that a poor team like the Oakland A’s could beat most rich teams simply by exploiting the inefficiencies. But—they went on to say—the author of Moneyball did not seem to realize the deeper reason for the inefficiencies in the market for baseball players: they sprang directly from the inner workings of the human mind. The ways in which some baseball expert might misjudge baseball players—the ways in which any expert’s judgments might be warped by the expert’s own mind—had been described, years ago, by a pair of Israeli psychologists, Daniel Kahneman and Amos Tversky. My book wasn’t original. It was simply an illustration of ideas that had been floating around for decades and had yet to be fully appreciated by, among others, me.

That was an understatement. Until that moment I don’t believe I’d ever heard of either Kahneman or Tversky, even though one of them had somehow managed to win a Nobel Prize in economics.

How did this pair of Israeli psychologists come to have so much to say about these matters of the human mind that they more or less anticipated a book about American baseball written decades in the future? What possessed two guys in the Middle East to sit down and figure out what the mind was doing when it tried to judge a baseball player, or an investment, or a presidential candidate? And how on earth does a psychologist win a Nobel Prize in economics?

Tversky in 1970.

Courtesy Of Barbara Tversky.

The dozen or so graduate students in Danny Kahneman’s seminar at Hebrew
University, in Jerusalem, were all surprised when, in the spring of
1969, Amos Tversky turned up. Danny never had guests: The seminar,
called Applications of Psychology, was his show. Amos’s interests were
about as far removed from the real-world problems in Applications of
Psychology as a psychologist’s could be.

Amos himself seemed about as far removed from Danny as he could be.
Danny had spent years of his childhood hiding in barns and chicken coops
in France, from the Nazis who hunted him. Amos was born and raised in a
society intent on making sure no Jewish child ever again would need to
hide from those who wished to kill him. Israel had made him a warrior. A
Spartan. Danny was deeply, painfully uncertain about himself. “His
defining emotion is doubt,” said one of his students. “And it is very
useful. Because it makes him go deeper and deeper and deeper.” Amos was
the most self-assured human being anyone knew.

The people who knew Amos and Danny best couldn’t imagine them getting
along with each other. “It was the graduate students’ perception that
they had some sort of rivalry,” said one of the students in the
Applications of Psychology seminar. “They were clearly the stars of the
department who somehow or other hadn’t gotten in sync.” And yet for
some reason Danny had invited Amos to come to his seminar to talk about
whatever he wanted to talk about. And, for some reason, Amos had
accepted.

Danny was a little surprised that Amos didn’t talk about his own
work—but then Amos’s work was so abstract and theoretical that he
probably decided it had no place in the seminar. Those who stopped to
think about it found it odd that Amos’s work betrayed so little interest
in the real world, when Amos was so intimately and endlessly engaged
with that world, and how, conversely, Danny’s work was consumed by
real-world problems, even as he kept other people at a distance.

Amos was now what people referred to, a bit confusingly, as a
“mathematical psychologist.” Non-mathematical psychologists, like
Danny, quietly viewed much of mathematical psychology as a series of
pointless exercises conducted by people who were using their ability to
do math as camouflage for how little of psychological interest they had
to say. Mathematical psychologists, for their part, tended to view
non-mathematical psychologists as simply too stupid to understand the
importance of what they were saying. Amos was then at work with a team
of mathematically gifted American academics on what would become a
three-volume, molasses-dense, axiom-filled textbook called Foundations
of Measurement—more than a thousand pages of arguments and proofs of
how to measure stuff. On the one hand, it was a wildly impressive
display of pure thought; on the other, the whole enterprise had a
tree-fell-in-the-woods quality to it. How important could the sound it
made be, if no one was able to hear it?

After the seminar, Amos and Danny had a few lunches together but then
headed off in separate directions. That summer Amos left for the United
States, and Danny for England, to continue his study of human attention.
He had all these ideas about the possible usefulness of this new
interest of his. In tank warfare, for instance. Danny was now taking
people into his research lab and piping one stream of digits into their
left ear and another stream of digits into their right ear, to test how
quickly they could switch their attention from one ear to the other, and
also how well they blocked their minds to sounds they were meant to be
ignoring. “In tank warfare, as in a Western shootout, the speed at
which one can decide on a target and act on that decision makes the
difference between life and death,” said Danny later. He might use his
test to identify which tank commanders could best orient their senses at
high speed—who among them might most quickly detect the relevance of a
signal, and focus his attention upon it, before he got blown to bits.

Dual Personalities

By the fall of 1969, Amos and Danny had both returned to Hebrew
University. During their joint waking hours, they could usually be found
together. Danny was a morning person, and so anyone who wanted him alone
could find him before lunch. Anyone who wanted time with Amos could
secure it late at night. In the intervening time, they might be glimpsed
disappearing behind the closed door of a seminar room they had
commandeered. From the other side of the door you could sometimes hear
them hollering at each other, but the most frequent sound to emerge was
laughter. Whatever they were talking about, people deduced, must be
extremely funny. And yet whatever they were talking about also felt
intensely private: Other people were distinctly not invited into their
conversation. If you put your ear to the door, you could just make out
that the conversation was occurring in both Hebrew and English. They
went back and forth—Amos, especially, always switched back to Hebrew
when he became emotional.

The students who once wondered why the two brightest stars of Hebrew
University kept their distance from each other now wondered how two so
radically different personalities could find common ground, much less
become soulmates. “It was very difficult to imagine how this chemistry
worked,” said Ditsa Kaffrey, a graduate student in psychology who
studied with them both.

Danny was always sure he was wrong. Amos was always sure he was right.
Amos was the life of every party; Danny didn’t go to the parties. Amos
was loose and informal; even when Danny made a stab at informality, it
felt as if he had descended from some formal place. With Amos you always
just picked up where you left off, no matter how long it had been since
you last saw him. With Danny there was always a sense you were starting
over, even if you had been with him just yesterday. Amos was tone-deaf
but would nevertheless sing Hebrew folk songs with great gusto. Danny
was the sort of person who might be in possession of a lovely singing
voice that he would never discover. Amos was a one-man wrecking ball for
illogical arguments; when Danny heard an illogical argument, he asked,
What might that be true of? Danny was a pessimist. Amos was not merely
an optimist; Amos willed himself to be optimistic, because he had
decided pessimism was stupid. When you are a pessimist and the bad thing
happens, you live it twice, Amos liked to say. Once when you worry about
it, and the second time when it happens. “They were very different
people,” said a fellow Hebrew University professor. “Danny was always
eager to please. He was irritable and short-tempered, but he wanted to
please. Amos couldn’t understand why anyone would be eager to please. He
understood courtesy, but eager to please—why?” Danny took everything
so seriously; Amos turned much of life into a joke. When Hebrew
University put Amos on its committee to evaluate all Ph.D. candidates,
he was appalled at what passed for a dissertation in the humanities.
Instead of raising a formal objection, he merely said, “If this
dissertation is good enough for its field, it’s good enough for me.
Provided the student can divide fractions!”

Beyond that, Amos was the most terrifying mind most people had ever
encountered. “People were afraid to discuss ideas in front of him,”
said a friend—because they were afraid he would put his finger on the
flaw that they had only dimly sensed. One of Amos’s graduate students,
Ruma Falk, said she was so afraid of what Amos would think of her
driving that when she drove him home, in her car, she insisted that he
drive. And now here he was spending all of his time with Danny, whose
susceptibility to criticism was so extreme that a single remark from a
misguided student sent him down a long, dark tunnel of self-doubt. It
was as if you had dropped a white mouse into a cage with a python and
come back later and found the mouse talking and the python curled in the
corner, rapt.

Kahneman (left) receives the Nobel Prize in Economic Sciences, 2002.

By Jonas Ekstromer/AFP.

But there was another story to be told, about how much Danny and Amos
had in common. Both were grandsons of Eastern European rabbis, for a
start. Both were explicitly interested in how people functioned when
they were in a “normal” unemotional state. Both wanted to do science.
Both wanted to search for simple, powerful truths. As complicated as
Danny may have been, he still longed to do “the psychology of single
questions,” and as complicated as Amos’s work may have seemed, his
instinct was to cut through endless bullshit to the simple nub of any
matter. Both men were blessed with shockingly fertile minds. And both
were Jews, in Israel, who did not believe in God. And yet all anyone saw
were their differences.

The most succinct physical manifestation of the deep difference between
the two men was the state of their offices. “Danny’s office was such a
mess,” recalled Daniela Gordon, who had become Danny’s teaching
assistant. “Scraps on which he’d scribbled a sentence or two. Paper
everywhere. Books everywhere. Books opened to places he’d stopped
reading. I once found my master’s thesis open on page 13—I think
that’s where he stopped. And then you would walk down the hall three or
four rooms, and you come to Amos’s office . . . and there is nothing
in it. A pencil on a desk. In Danny’s office you couldn’t find anything
because it was such a mess. In Amos’s office you couldn’t find anything
because there was nothing there.” All around them people watched and
wondered: Why were they getting along so well? “Danny was a
high-maintenance person,” said one colleague. “Amos was the last one
to put up with a high-maintenance person. And yet he was willing to go
along. Which was amazing.”

Danny and Amos didn’t talk much about what they got up to when they were
alone together, which just made everyone else more curious about what it
was. In the beginning they were kicking around Danny’s
proposition—that people didn’t depend on probability or statistics.
Whatever human beings did when presented with a problem that had a
statistically correct answer, it wasn’t statistics. But how did you sell
that to an audience of professional social scientists who were more or
less blinded by theory? And how did you test it? They decided, in
essence, to invent an unusual statistics test, give it to the
scientists, and see how they performed. Their case would be built from
evidence that consisted entirely of answers to questions they’d put to
some audience—in this case, an audience of people trained in
statistics and probability theory. Danny dreamed up most of the
questions, such as:

The mean I.Q. of the population of eighth-graders in a city is known to
be 100. You have selected a random sample of 50 children for a study of
educational achievement. The first child tested has an I.Q. of 150. What
do you expect the mean I.Q. to be for the whole sample? (This test was
meant to explore how new information affects decision-making.)

At the end of the summer of 1969, Amos took Danny’s questions to the
annual meeting of the American Psychological Association, in Washington,
D.C., and then on to a conference of mathematical psychologists. There
he gave the tests to roomfuls of people whose careers required fluency
in statistics. Two of the test takers had written statistics textbooks.
Amos then collected the completed tests and flew home with them to
Jerusalem.

“THEIR RELATIONSHIP WAS MORE INTENSE THAN A MARRIAGE,” SAYS TVERSKY’S
WIFE.

There he and Danny sat down to write together for the first time. Their
offices were tiny, so they worked in a small seminar room. Amos didn’t
know how to type, and Danny didn’t particularly want to, so they sat
with notepads. They went over each sentence time and again and wrote, at
most, a paragraph or two each day. “I had this sense of realization:
Ah, this is not going to be the usual thing, this is going to be
something else,” said Danny. “Because it was funny.”

When Danny looked back on that time, what he recalled mainly was the
laughter—what people outside heard emanating from the seminar room.
“I have the image of balancing precariously on the back legs of a chair
and laughing so hard I nearly fell backwards.” The laughter may have
sounded a bit louder when the joke had come from Amos, but that was only
because Amos had a habit of laughing at his own jokes. (“He was so
funny that it was O.K. he was laughing at his own jokes.”) In Amos’s
company Danny felt funny, too—and he’d never felt that way before. In
Danny’s company Amos, too, became a different person: uncritical. Or, at
least, uncritical of whatever came from Danny. He didn’t even poke fun
in jest. He enabled Danny to feel, in a way he hadn’t before, confident.
Maybe for the first time in his life Danny was playing offense. “Amos
did not write in a defensive crouch,” he said. “There was something
liberating about the arrogance—it was extremely rewarding to feel like
Amos, smarter than almost everyone.” The finished paper dripped with
Amos’s self-assurance, beginning with the title he had put on it:
“Belief in the Law of Small Numbers.” And yet the collaboration was so
complete that neither of them felt comfortable taking the credit as the
lead author; to decide whose name would appear first, they flipped a
coin. Amos won.

When they wrote their first papers, Danny and Amos had no particular
audience in mind. Their readers would be the handful of academics who
happened to subscribe to the highly specialized psychology trade
journals in which they published. By 1972 they had spent the better part
of three years uncovering the ways in which people judged and
predicted—but the examples that they had used to illustrate their
ideas were all drawn directly from psychology, or from the strange,
artificial-seeming tests that they had given high-school and college
students. Yet they were certain that their insights applied anywhere in
the world that people were judging probabilities and making decisions.
They sensed that they needed to find a broader audience. “The next
phase of the project will be devoted primarily to the extension and
application of this work to other high-level professional activities,
e.g., economic planning, technological forecasting, political decision
making, medical diagnosis, and the evaluation of legal evidence,” they
wrote in a research proposal. They hoped, they wrote, that the decisions
made by experts in these fields could be “significantly improved by
making these experts aware of their own biases, and by the development
of methods to reduce and counteract the sources of bias in judgment.”
They wanted to turn the real world into a laboratory. It was no longer
just students who would be their lab rats but also doctors and judges
and politicians. The question was: How to do it?

In 1972, Irv Biederman, then a visiting associate professor of
psychology at Stanford University, heard Danny give a talk about
heuristics and biases on the Stanford campus. “I remember I came home
from the talk and told my wife, ‘This is going to win a Nobel Prize in
economics,’ ” recalled Biederman. “I was so absolutely convinced.
This was a psychological theory about economic man. I thought, What
could be better? Here is why you get all these irrationalities and
errors. They come from the inner workings of the human mind.”

They couldn’t help but sense a growing interest in their work. “That
was the year it was really clear we were onto something,” recalled
Danny. “People started treating us with respect.” But by the fall of
1973 it was fairly clear to Danny that other people would never fully
understand his relationship with Amos. The previous academic year,
they’d taught a seminar together at Hebrew University. From Danny’s
point of view, it had been a disaster. The warmth he felt when he was
alone with Amos vanished whenever Amos was in the presence of an
audience. “When we were with other people we were one of two ways,”
said Danny. “Either we finished each other’s sentences and told each
other’s jokes. Or we were competing. No one ever saw us working
together. No one knows what we were like.” What they were like, in
every way but sexually, was lovers. They connected with each other more
deeply than either had connected with anyone else. Their wives noticed
it. “Their relationship was more intense than a marriage,” said
Tversky’s wife, Barbara. “I think they were both turned on
intellectually more than either had ever been before. It was as if they
were both waiting for it.” Danny sensed that his wife felt some
jealousy; Amos actually praised Barbara, behind her back, for dealing so
gracefully with the intrusion on their marriage. “Just to be with
him,” said Danny. “I never felt that way with anyone else, really. You
are in love and things. But I was rapt. And that’s what it was like. It
was truly extraordinary.”

And yet it was Amos who worked hardest to find ways to keep them
together. “I was the one who was holding back,” said Danny. “I kept
my distance because I was afraid of what would happen to me without
him.”

An Israeli tank during the 1973 Yom Kippur War.

By David Rubinger/The Life Images Collection/Getty Images.

The Psychology of War

It was four in the morning California time on October 6, 1973, when the
armies of Egypt and Syria launched their attack upon Israel. They’d
taken the Israelis by surprise on Yom Kippur. Along the Suez Canal, the
500-man Israeli garrison was overwhelmed by 100,000 or so Egyptian
troops. From the Golan Heights, 177 Israeli tank crews gazed down upon
an attacking force of 2,000 Syrian tanks. Amos and Danny, still in the
United States trying to become decision analysts, raced to the airport
and got the first flight possible to Paris, where Danny’s sister worked
in the Israeli Embassy. Getting into Israel during a war wasn’t easy.
Every inbound El Al plane was crammed with fighter pilots and
combat-unit commanders who were coming in to replace the men killed in
the first days of the invasion. That’s just what you did if you were an
Israeli capable of fighting in 1973: You ran toward the war. Knowing
this, Egyptian president Anwar Sadat had promised to shoot down any
commercial planes attempting to land in Israel. As they waited in Paris
for Danny’s sister to talk someone into letting them onto a flight,
Danny and Amos bought combat boots. They were made of canvas—lighter
than the leather boots issued by the Israeli military.

When the war broke out, Barbara Tversky was on the way to an emergency
room in Jerusalem with her eldest son. He had won a contest with his
brother to see who could stick a cucumber farther up his own nose. As
they headed home, people surrounded their car and screamed at Barbara
for being on the road. The country was in a state of panic: fighter jets
screamed low over Jerusalem to signal all reserves to return to their
units. Hebrew University closed. Army trucks rumbled all night through
the Tverskys’ usually tranquil neighborhood. The city was black.
Streetlamps remained off; anyone who owned a car taped over its brake
lights. The stars could not have been more spectacular, or the news more
troubling—because, for the first time, Barbara sensed that the Israeli
government was withholding the truth. This war was different from the
others: Israel was losing. Not knowing where Amos was, or what he
planned to do, didn’t help. Phone calls were so expensive that when he
was in the United States they communicated only by letter. Her situation
wasn’t unusual: there were Israelis who would learn that loved ones
living abroad had returned to Israel to fight only by being informed
that they had been killed in action.

To make herself useful, Barbara went to the library and found the
material to write a newspaper article about stress and how to cope with
it. A few nights into the conflict, around 10 o’clock, she heard
footsteps. She was working alone in the study, with the blinds lowered,
to avoid letting the light seep out. The kids were asleep. Whoever was
coming up the stairs was running; then suddenly Amos bounded from the
darkness. The El Al flight that he had taken with Danny had carried as
passengers no one but Israeli men returning to fight. It had descended
into Tel Aviv in total darkness: There hadn’t even been a light on the
wing. Once again, Amos went into the closet and pulled down his old army
uniform, which he wore in the 1967 Six Day War, now with a captain’s
insignia on it. It still fit. At five o’clock the following morning he
left.

He had been assigned, with Danny, to the psychology field unit. The unit
had grown since the mid-1950s, when Danny had redesigned the selection
system. In early 1973 an American psychologist named James Lester, sent
by the Office of Naval Research to study Israeli military psychology,
wrote a report in which he described the unit Danny and Amos were about
to join. Lester marveled at the entire society—a country that had at
once the world’s strictest driving tests and the world’s highest
automobile accident rates—but seems to have been struck especially by
the faith the Israeli military placed in their psychologists. “Failure
rate in the officer course is running at 15–20%,” he wrote. “Such
confidence does the military have in the mysteries of psychological
research that they are asking the Selection Section to try to identify
these 15% during the first week in training.”

The head of Israeli military psychology, Lester reported, was an oddly
powerful character named Benny Shalit. Shalit had argued for, and
received, a new, elevated status for military psychology. His unit had a
renegade quality to it; Shalit had gone so far as to sew an insignia of
his own design onto its uniform. It consisted of the Israeli olive
branch and sword, Lester explained, “topped by an eye which symbolizes
assessment, insight, or something along those lines.” In his attempts
to turn his psychology unit into a fighting force, Shalit had dreamed up
ideas that struck even the psychologists as wacko. Hypnotizing Arabs and
sending them to assassinate Arab leaders, for instance. “He actually
did hypnotize one Arab,” recalled Daniela Gordon, who served under
Shalit in the psychology unit. “They took him to the Jordanian border,
and he just ran off.”

A rumor among Shalit’s subordinates—and it refused to die—was that
Shalit kept the personality assessments made of all the Israeli-military
big shots, back when they were young men entering the army, and let them
know that he wouldn’t be shy about making them public. Whatever the
reason, Benny Shalit had an unusual ability to get his way in the
Israeli military. And one of the unusual things Shalit had asked for,
and received, was the right to embed psychologists in army units, where
they might directly advise commanders. “Field psychologists are in a
position to make recommendations on a variety of unconventional
issues,” Lester reported to his U.S. Navy superiors. “For example, one
noticed that infantry troops in hot weather, stopping to open soft
drinks with their ammunition magazines, often damaged the stock. It was
possible to redesign the stock so that a tool for opening bottles was
included.” Shalit’s psychologists had eliminated the unused sights on
submachine guns, and changed the way machine-gun units worked together,
to increase the rate at which they fired. Psychologists in the Israeli
Army were, in short, off the leash. “Military psychology is alive and
well in Israel,” concluded the United States Navy’s reporter on the
ground. “It is an interesting question whether or not the psychology of
the Israelis is becoming a military one.”

Tversky and Kahneman in Tversky’s backyard.

By May Bar-Hillel.

What Benny Shalit’s field psychologists might do during an actual
battle, however, was unclear. “The psychology unit did not have the
faintest idea what to do,” said Eli Fishoff, who served as Benny
Shalit’s second-in-command. “The war was totally unexpected. We were
just thinking, Maybe it’s the end of us.” In a matter of days the
Israeli Army had lost more men, as a percentage of the population, than
the United States military lost in the entire Vietnam War. The war was
later described by the Israeli government as a “demographic disaster”
because of the prominence and talent of the Israelis who were killed. In
the psychology unit someone came up with the idea of designing a
questionnaire to determine what, if anything, might be done to improve
the morale of the troops. Upon his arrival at the psychology unit Amos
seized upon it, helped to design the questions, and then used the entire
exercise more or less as an excuse to get himself closer to the action.
“We just got a jeep and went bouncing around in the Sinai looking for
something useful to do,” said Danny.

Their fellow psychologists who watched Danny and Amos toss rifles into
the back of a jeep and set out for the battlefield thought they were out
of their minds. “Amos was so excited—like a little child,” recalled
Yaffa Singer, who worked with Danny in the Israeli Army’s psychology
unit. “But it was crazy for them to go to the Sinai. It was so
dangerous. It was absolutely crazy to send them out with those
questionnaires.” The risk of running directly into enemy tanks and
planes was the least of it. There were land mines everywhere; it was
easy to get lost. “They didn’t have guards,” said Daniela Gordon,
their commanding officer. “They guarded themselves.” All of them felt
less concern for Amos than for Danny. “We were very worried about
sending Danny on his own,” said Eli Fishoff, head of the field
psychologists. “I wasn’t so worried about Amos—because Amos was a
fighter.”

The moment Danny and Amos were in the jeep roaring through the Sinai,
however, it was Danny who became useful. “He was jumping off the car
and grilling people,” recalled Fishoff. Amos seemed like the practical
one, but Danny, more than Amos, had a gift for finding solutions to
problems where others failed even to notice that there was a problem to
solve. As they sped toward the front lines, Danny noticed the huge piles
of garbage on the roadsides: the leftovers from the canned meals
supplied by the U.S. Army. He examined what the soldiers had eaten and
what they had thrown out. (They liked the canned grapefruit.) His
subsequent recommendation that the Israeli Army analyze the garbage and
supply the soldiers with what they actually wanted made newspaper
headlines.

Israeli tank drivers were just then being killed in action at an
unprecedented rate. Danny visited the site where new tank drivers were
being trained, as quickly as possible, to replace the ones who had died.
Groups of four men took turns in two-hour shifts on a tank. Danny
pointed out that people learn more efficiently in short bursts, and that
new tank drivers might be educated faster if the trainees rotated behind
the wheel every 30 minutes. He also somehow found his way to the Israeli
Air Force. Fighter pilots were also dying in unprecedented numbers
because of Egypt’s use of new and improved surface-to-air missiles
provided by the Soviet Union. One squadron had suffered especially
horrific losses. The general in charge wanted to investigate, and
possibly punish, the unit. “I remember him saying accusingly that one
of the pilots had been hit ‘not only by one missile but by four!’ As if
that was conclusive evidence of the pilot’s ineptitude,” recalled
Danny.

Danny explained to the general that he had a sample-size problem: the
losses experienced by the supposedly inept fighter squadron could have
occurred by random chance alone. If he investigated the unit, he would
no doubt find patterns in behavior that might serve as an explanation.
Perhaps the pilots in that squadron had paid more visits to their
families, or maybe they wore funny-colored underpants. Whatever he found
would be a meaningless illusion, however. There weren’t enough pilots in
the squadron to achieve statistical significance. On top of it, an
investigation, implying blame, would be horrible for morale. The only
point of an inquiry would be to preserve the general’s feelings of
omnipotence. The general listened to Danny and stopped the inquiry. “I
have considered that my only contribution to the war effort,” said
Danny.

The actual business at hand—putting questions to soldiers fresh from
combat—Danny found pointless. Many of them were traumatized. “We were
wondering what to do with people who were in shock—how even to
evaluate them,” said Danny. “Every soldier was frightened, but there
were some people who couldn’t function.” Shell-shocked Israeli soldiers
resembled people with depression. There were some problems he didn’t
feel equipped to deal with, and this was one of them.

He didn’t really want to be in the Sinai anyway, not in the way Amos
seemed to want to be there. “I remember a sense of futility—that we
were wasting our time there,” he said. When their jeep bounced once too
often and caused Danny’s back to go out, he quit the journey—and left
Amos alone to administer the questionnaires. From their jeep rides he
retained a single vivid memory. “We went to sleep near a tank,” he
recalled. “On the ground. And Amos didn’t like where I was sleeping,
because he thought the tank might move and crush me. And I remember
being very, very touched by this. It was not sensible advice. A tank
makes a lot of noise. But that he was worried about me.”

Later, the Walter Reed Army Institute of Research undertook a study of
the war. “Battle Shock Casualties During the 1973 Arab-Israeli War,”
it was called. The psychiatrists who prepared the report noted that the
war was unusual in its intensity—it was fought 24 hours a day, at
least at the start—and in the losses suffered. The report also noted
that, for the first time, Israeli soldiers were diagnosed with
psychological trauma. The questionnaires Amos had helped to design asked
the soldiers many simple questions: Where were you? What did you do?
What did you see? Was the battle a success? If not, why not? “People
started to talk about fear,” recalls Yaffa Singer. “About their
emotions. From the War of Independence until 1973 it hadn’t been
allowed. We are supermen. No one has the guts to talk about fear. If we
talk about it, maybe we won’t survive.”

For days after the war, Amos sat with Singer and two other colleagues in
the psychology field unit and read through the soldiers’ answers to his
questions. The men spoke of their motives for fighting. “It’s such
horrible information that people tend to bury it,” said Singer. But
caught fresh, the soldiers revealed to the psychologists sentiments
that, in retrospect, seemed blindingly obvious. “We asked, Why is
anyone fighting for Israel?” said Singer. “Until that moment we were
just patriots. When we started reading the questionnaires it was so
obvious: They were fighting for their friends. Or for their families.
Not for the nation. Not for Zionism. At the time it was a huge
realization.” Perhaps for the first time, Israeli soldiers spoke openly
of their feelings as they watched five of their beloved platoon-mates
blown to bits or as they saw their best friend on earth killed because
he turned left when he was supposed to turn right. “It was
heartbreaking to read them,” said Singer.

Right up until the fighting stopped, Amos sought risks that he didn’t
need to take—that in fact others thought were foolish to take. “He
decided to witness the end of the war along the Suez,” recalled
Barbara, “even though he knew full well that shelling continued after
the time of the cease-fire.” Amos’s attitude toward physical risk
occasionally shocked even his wife. Once, he announced that he wanted to
start jumping out of airplanes again, just for fun. “I said, ‘You are
the father of children,’ ” said Barbara. “That ended the
discussion.” Amos wasn’t a thrill-seeker, exactly, but he had strong,
almost child-like passions that, every so often, he allowed to grab hold
of him and take him places most people would never wish to go.

In the end, he crossed the Sinai to the Suez Canal. Rumors circulated
that the Israeli Army might march all the way to Cairo, and that Soviets
were sending nuclear weapons to Egypt to prevent them from doing so.
Arriving at the Suez, Amos found that the shelling hadn’t merely
continued; it had intensified. There was now a long-standing tradition,
on both sides of any Arab-Israeli war, of seizing the moment immediately
before a formal cease-fire to fire any remaining ammunition at each
other. The spirit of the thing was: Kill as many of them as you can,
while you can. Wandering around near the Suez Canal and sensing an
incoming missile, Amos leapt into a trench and landed on top of an
Israeli soldier.

Are you a bomb? asked the terrified soldier. No, I’m Amos, said Amos. So
I’m not dead? asked the soldier. You’re not dead, said Amos. That was
the one story Amos told. Apart from that, he seldom mentioned the war
again.

You Can Lead a Horse to Water

In late 1973 or early 1974, Danny gave a talk, which he would deliver
more than once, and which he called “Cognitive Limitations and Public
Decision Making.” It was troubling to consider, he began, “an organism
equipped with an affective and hormonal system not much different from
that of the jungle rat being given the ability to destroy every living
thing by pushing a few buttons.” Given the work on human judgment that
he and Amos had just finished, he found it further troubling to think
that “crucial decisions are made, today as thousands of years ago, in
terms of the intuitive guesses and preferences of a few men in positions
of authority.” The failure of decision-makers to grapple with the inner
workings of their own minds, and their desire to indulge their gut
feelings, made it “quite likely that the fate of entire societies may
be sealed by a series of avoidable mistakes committed by their
leaders.”

Before the war, Danny and Amos had shared the hope that their work on
human judgment would find its way into high-stakes real-world
decision-making. In this new field, called decision analysis, they could
transform high-stakes decision-making into a sort of engineering
problem. They would design decision-making systems. Experts on
decision-making would sit with leaders in business, the military, and
government and help them to frame every decision explicitly as a gamble,
to calculate the odds of this or that happening, and to assign values to
every possible outcome.

If we seed the hurricane, there is a 50 percent chance we lower its wind
speed but a 5 percent chance that we lull people who really should
evacuate into a false sense of security: What do we do?

In the bargain, the decision analysts would remind important
decision-makers that their gut feelings had mysterious powers to steer
them wrong. “The general change in our culture toward numerical
formulations will give room for explicit reference to uncertainty,”
Amos wrote in notes to himself for a talk of his own. Both Amos and
Danny thought that voters and shareholders and all the other people who
lived with the consequences of high-level decisions might come to
develop a better understanding of the nature of decision-making. They
would learn to evaluate a decision not by its outcomes—whether it
turned out to be right or wrong—but by the process that led to it. The
job of the decision-maker wasn’t to be right but to figure out the odds
in any decision and play them well. As Danny told audiences in Israel,
what was needed was a “transformation of cultural attitudes to
uncertainty and to risk.”

Exactly how some decision analyst would persuade any business, military,
or political leader to allow him to edit his thinking was unclear. How
would you even persuade some important decision-maker to assign numbers
to his “utilities” (that is, personal value as opposed to objective
value)? Important people didn’t want their gut feelings pinned down,
even by themselves. And that was the rub.

Later, Danny recalled the moment he and Amos lost faith in decision
analysis. The failure of Israeli intelligence to anticipate the Yom
Kippur attack led to an upheaval in the Israeli government and a
subsequent brief period of introspection. They’d won the war, but the
outcome felt like a loss. The Egyptians, who had suffered even greater
losses, were celebrating in the streets as if they had won, while
everyone in Israel was trying to figure out what had gone wrong. Before
the war, the Israeli intelligence unit had insisted, despite a lot of
evidence to the contrary, that Egypt would never attack Israel as long
as Israel maintained air superiority. Israel had maintained air
superiority, and yet Egypt had attacked. After the war, with the view
that perhaps it could do better, Israel’s Ministry of Foreign Affairs
set up its own intelligence unit. The man in charge of it, Zvi Lanir,
sought Danny’s help. In the end, Danny and Lanir conducted an elaborate
exercise in decision analysis. Its basic idea was to introduce a new
rigor in dealing with questions of national security. “We started with
the idea that we should get rid of the usual intelligence report,” said
Danny. “Intelligence reports are in the form of essays. And essays have
the characteristic that they can be understood any way you damn well
please.” In place of the essay, Danny wanted to give Israel’s leaders
probabilities, in numerical form.

In 1974, U.S. secretary of state Henry Kissinger had served as the
middleman in peace negotiations between Israel and Egypt and between
Israel and Syria. As a prod to action, Kissinger had sent the Israeli
government the C.I.A.’s assessment that, if the attempt to make peace
failed, very bad events were likely to follow. Danny and Lanir set out
to give Israeli foreign minister Yigal Allon precise numerical estimates
of the likelihood of some very specific bad things happening. They
assembled a list of possible “critical events or concerns”: regime
change in Jordan, U.S. recognition of the Palestinian Liberation
Organization, another full-scale war with Syria, and so on. They then
surveyed experts and well-informed observers to establish the likelihood
of each event. Among these people, they found a remarkable consensus:
there wasn’t a lot of disagreement about the odds. When Danny asked the
experts what the effect might be of the failure of Kissinger’s
negotiations on the probability of war with Syria, for instance, their
answers clustered around “raises the chance of war by 10 percent.”

Danny and Lanir then presented their probabilities to Israel’s Foreign
Ministry. (“The National Gamble,” they called their report.) Foreign
Minister Allon looked at the numbers and said, “Ten percent increase?
That is a small difference.”

Danny was stunned: if a 10 percent increase in the chances of full-scale
war with Syria wasn’t enough to interest Allon in Kissinger’s peace
process, how much would it take to turn his head? That number
represented the best estimate of the odds. Apparently, the foreign
minister didn’t want to rely on the best estimates. He preferred his own
internal probability calculator: his gut. “That was the moment I gave
up on decision analysis,” said Danny. “No one ever made a decision
because of a number. They need a story.” As Danny and Lanir wrote,
decades later, after the U.S. Central Intelligence Agency asked them to
describe their experience in decision analysis, the Israeli Foreign
Ministry was “indifferent to the specific probabilities.” What was the
point of laying out the odds of a gamble if the person taking it either
didn’t believe the numbers or didn’t want to know them? The trouble,
Danny suspected, was that “the understanding of numbers is so weak that
they don’t communicate anything. Everyone feels that those probabilities
are not real—that they are just something on somebody’s mind.”

In the history of Danny and Amos, there are periods when it is difficult
to disentangle their enthusiasm for their ideas from their enthusiasm
for each other. The moments before and after the Yom Kippur War appear,
in hindsight, less like a natural progression from one idea to the next
than two men in love scrambling to find an excuse to be together. They
felt they had finished exploring the errors that arose from the rules of
thumb people use to evaluate probabilities in any uncertain situation.
They’d found decision analysis promising but ultimately futile. They
went back and forth on writing a general-interest book about the various
ways the human mind deals with uncertainty; for some reason, they could
never get beyond a sketchy outline and false starts of a few chapters.
After the Yom Kippur War—and the ensuing collapse of the public’s
faith in the judgment of Israeli government officials—they thought
that what they really should do was reform the educational system so
that future leaders were taught how to think. “We have attempted to
teach people to be aware of the pitfalls and fallacies of their own
reasoning,” they wrote, in a passage for the popular book that never
came to be. “We have attempted to teach people at various levels in
government, army etc. but achieved only limited success.”